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Outer Sphere Urea Hydrolysis by Bis-Nickel Complexes: Questioning the Urea Activation by the Urease Enzyme

preprint
submitted on 12.06.2019 and posted on 13.06.2019 by Caterina Gruenwaldt Cunha Marques Netto, Christian O. Martins, Letícia K. Sebastiany, Alejandro López-Castillo, Rafael S. Freitas, LEANDRO H. ANDRADE, Henrique E. Toma
Urease enzyme has a dinuclear nickel active centre that hydrolyze urea into carbon dioxide and ammonia. In this work, two bis-nickel urease models were synthesized, [Ni2L(OAc)] and [Ni2L(Cl)(Et3N)2], based on the Trost bis-Pro0Phenol ligand (L). Interestingly, both complexes produced ammonia from urea, in which the [Ni2L(OAc)] complex was ten times slower than urease, whereas the more labile complex [Ni2L(Cl)(Et3N)2],was only four times slower. The intermediates were evaluated both experimentally and theoretically, indicating that the [Ni2L(H2O)2]+ intermediate is the most important to activate urea via an outersphere mechanism. Isocyanate was produced in a self-elimination mechanism. The reaction performed with different substrates indicated that the biomimetic complexes were able to hydrolyze isocyanate. The outersphere activation of urea by these complexes reals an alternative activation mechanism to be considered for the urease enzyme, not yet reported in the literature. .

Funding

CAPES 001

CNPq 141313/2017-0

FAPESP 2008/10177-7

FAPESP 2014/22332-8

FAPESP 2016/01622-3

FAPESP 2016/17592-6

FAPESP 2010/11385-2

FAPESP 2004/10235-6

History

Email Address of Submitting Author

caterina@ufscar.br

Institution

Universidade Federal de São Carlos (UFSCar)

Country

Brazil

ORCID For Submitting Author

0000-0002-3285-4129

Declaration of Conflict of Interest

There is no conflict of interest.

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